docs: def main():
      """ Main entry point of the CLI. """
      try:
          args = sys.argv[1:]
  
          try:
              _, args = getopt.getopt(args, MAIN_OPTS, MAIN_LONG_OPTS)
          except getopt.GetoptError as e:
              error(str(e))
              sys.exit(1)
  
          if args[0] == 'prompt':
              try:
                  from topydo.ui.prompt.Prompt import PromptApplication
                  PromptApplication().run()
              except ImportError:
                  error("Some additional dependencies for prompt mode were not installed, please install with 'pip3 install topydo[prompt]'")
          elif args[0] == 'columns':
              try:
                  from topydo.ui.columns.Main import UIApplication
                  UIApplication().run()
              except ImportError:
                  error("Some additional dependencies for column mode were not installed, please install with 'pip3 install topydo[columns]'")
              except NameError as err:
                  if _WINDOWS:
                      error("Column mode is not supported on Windows.")
                  else:
                      error("Could not load column mode: {}".format(err))
          else:
              CLIApplication().run()
      except IndexError:
          CLIApplication().run()